Bottled wine often has tartar precipitates in the form of crystals on the bottom of the bottle. Such precipitates occur between bottling and consumption. These precipitates make the product unattractive to consumers.
Various methods have been proposed for preventing tartar precipitates. Tartar precipitates have been removed by cooling, cation exchange, anion exchange, reverse osmosis, and electrodialysis. Also, tartar precipitates have been inhibited by the use of additives.
Of the above methods, the cooling methods have been commonly used. The other methods have not been used commercially, since they suffer from various disadvantages.
A cooling method based on the primary nucleation of potassium hydrogentartrate which is a major component of tartar, is known. However, this method requires the maintenance of supersaturated solutions by means of cooling for a long time to produce natural nucleation. Thus, it cannot serve market demand immediately, and it requires a large initial investment for cooling equipment and storage equipment.
Another cooling method is known which comprises increasing tartar concentration by freezing and thickening wine to accelerate crystallization. However, this method cannot steadily crystallize and remove tartar and requires additional freezing equipment. This still further increases initial equipment cost.
To eliminate the above disadvantages, some cooling methods have been proposed that comprise adding tartar seed crystals to a source liquid of wine so as to cause secondary nucleation and grow tartar crystals in the source liquid, and thereafter separating the tartar crystals. These seeding methods are divided into two categories: A first contact method and a second carrier adhesion method. The first method is disclosed, for example, in West German Patent DE No. 3244221C1 issued to Westfalia Co. This publication discloses a process in which seed crystals of potassium hydrogentartrate and dipotassium DL-tartrate are also added to precipitate and remove calcium ions which inhibit the growth of tartar crystals. In Japanese Examined Patent Publication No. 39157/1982, issued to Henkel and Co., a process is disclosed in which calcium carbonate is employed together with the seed crystal material. The second method is disclosed, for example, in Japanese Examined Patent Publication No. 5157/1981, issued to Henkel and Co. This publication discloses a process in which tartar is extracted from wine through the adhesion of the tartar on carriers made of fiber, etc. The carriers carry the tartar crystals to promote the extraction.
In the seeding methods, tartar dissolved in a source liquid is crystallized with seed crystals, and then the resulting suspension is separated into treated liquid and tartar crystals by use of mechanical separation means such as hydrocyclones, centrifuges and filters. The treated liquid is served as a product. A part of the tartar crystals is recycled and utilized as seed crystals.
In these methods, the suspension in which tartar which has been precipitated together with seed crystals in a reaction vessel, is introduced into separation means together with treated liquid, and then is separated. In other words, these methods are batch processes wherein whenever a treatment is conducted, a source liquid has to be introduced into the reaction vessel and seed crystals also have to be added to the source liquid. Therefore, these methods require a large amount of seed crystals and thus require separation means having a large capacity such as a centrifuge. Further, these methods based on the batch process are not advantageous to operation or equipment, i.e., they require a large-sized crystallizer or a number of crystallizers in order to treat a large amount of source liquid.
Usually, the suspension is stood for about two weeks so as to precipitate tartar crystals. In order to shorten such period for the precipitation, Japanese Examined Patent Publication No. 39157/1982 issued to Henkel and Co. suggests a continuous process wherein the suspension is stood for 1 to 2 days, and thereafter supernatant is discharged by use of auxiliary mechanical means. The process, however, additionally requires contact crystals to promote the precipitation of calcium tartrate resulting from the reaction of calcium carbonate and tartaric acid. It also requires a heating stage for promoting the reaction and requires the installation of intermediate plates and means for collecting gas generated in the crystallizing vessel. Therefore, it is apparent that the process requires complicated equipment and operation.
Japanese Examined Patent Publication No. 5157/1981 issued to Henkel and Co. also suggests an apparatus which comprises a crystallizing vessel and a carrier which is as large as possible for installing it in the crystallizing vessel, pulverized seed crystals preliminarily adhering to said carrier, means for scraping crystallized tartar during the process, and a conveyor which discharges precipitated tartar. However, this system is also complicated and is not advantageous to operation, equipment or maintenance.
For the purpose of solving the above-described problems of the seeding methods and making it possible to efficiently and continuously conduct a seeding method without a batch process or large equipment, the present inventors suggested a draft tube baffled crystallizer (hereinafter referred to as DTB crystallizer) in Japanese Unexamined Patent Publication No. 69976/1987.
As shown in FIG. 3 of the accompanied drawings, the DTB crystallizer 100 comprises a cylindrical vessel 101 which has an outlet 102 on its upper wall and an inlet 103 at its bottom, a draft tube 104 which is centered in a lower half portion of the vessel 101 and supported by supporting members 105, 105', a stirrer which comprises a shaft 106 extending along with the longitudinal axis of the vessel 101, propellers 107, 107' mounted on the shaft 106 inside the draft tube 104 and a propeller 108 mounted on the shaft 106 below the draft tube 104, and a cooling jacket 109 which is disposed on the exterior wall of the vessel 101.
The DTB crystallizer attains three functions of crystallization, classification and clarification in a vessel by forming the following two sections in the vessel in use. The first is a crystallization section wherein a source liquid is circulated along the draft tube at a low temperature so that tartar is crystallized involving seed crystals as nuclei. The second is a calm section which is located in the upper portion of the crystallizer and is not disturbed by the circulation of the crystallization section. The classification function is effected between the crystallization section and the calm section by allowing crystals to sink from the calm section to the crystallization section. The DTB crystallizer is simple in structure, low in cost and easy to maintain, and makes it possible to continuously separate tartar from a source liquid of wine or grape juice in a short time.
However, the rate of production has to be limited in order to form the two sections and maintain the functions of crystallization, classification and clarification in the DTB crystallizer. If the amount of a source liquid is increased in a continuous operation, the circulation along the draft tube extends to the calm section so that tartar contaminates the treated liquid and the treated liquid becomes chemically unstabilized.
The DTB crystallizer would be replaced with another large-scaled similar crystallizer rather than modified if the production capacity should be increased.